Electric-motor control device, system and method

Abstract

Provided is an electric-motor control device, including: a command value calculation unit configured to calculate a command value directed to an electric motor based on a command value and a given moment-of-inertia value; a difference detection unit configured to detect a difference between the moment-of-inertia value and an estimated moment-of-inertia value; a moment-of-inertia value change unit configured to change at least anyone of the moment-of-inertia value and a correction coefficient for the moment-of-inertia value based on the difference; and a change restriction unit configured to restrict a change in the moment-of-inertia value or the correction coefficient when at least any one of the moment-of-inertia value and the correction coefficient is changed to decrease by the moment-of-inertia value change unit.

The invention claimed is: 
     
       1. An electric-motor control device, comprising:
 a command value calculation unit configured to calculate a command value directed to an electric motor based on a command value and a given moment-of-inertia value; 
 a difference detection unit configured to detect a difference between the given moment-of-inertia value and an estimated moment-of-inertia value; 
 a moment-of-inertia value change unit configured to change at least any one of the given moment-of-inertia value and a correction coefficient for the given moment-of-inertia value based on the difference; and 
 a change restriction unit configured to restrict a change in the given moment-of-inertia value or the correction coefficient when at least any one of the given moment-of-inertia value and the correction coefficient is decreased by the moment-of-inertia value change unit. 
 
     
     
       2. The electric-motor control device according to  claim 1 , wherein the change restriction unit is configured to restrict the change in at least any one of the given moment-of-inertia value and the correction coefficient based on a condition relating to stability of a value of the detected difference after at least any one of the given moment-of-inertia value and the correction coefficient is decreased by the moment-of-inertia value change unit. 
     
     
       3. The electric-motor control device according to  claim 2 , wherein:
 the difference comprises a ratio of the estimated moment-of-inertia value to the given moment-of-inertia value; and 
 the condition includes a condition relating to a gradient of a fluctuation of the difference with respect to time. 
 
     
     
       4. The electric-motor control device according to  claim 3 , wherein the condition includes a case in which the gradient is positive. 
     
     
       5. The electric-motor control device according to  claim 3 , if wherein the condition includes a case in which the gradient continues to be negative after at least any one of the given moment-of-inertia value and the correction coefficient Is decreased. 
     
     
       6. The electric-motor control device according to  claim 4 , wherein the condition includes a case in which the gradient continues to be negative after at least any one of the given moment-of-inertia value and the correction coefficient is decreased. 
     
     
       7. The electric-motor control device ac cording to  claim 3 , wherein the condition includes a case in which a predetermined period has not elapsed after at least any one of the given moment-inertia value and the correction coefficient is decreased. 
     
     
       8. The electric-motor control device according to  claim 4 , wherein the condition includes a case in which a predetermined period has not elapsed after at least any one of the given moment-of-inertia value and the correction coefficient is decreased. 
     
     
       9. The electric-motor control device according to  claim 5 , wherein the condition includes a case in which a predetermined period has not elapsed after at least any one of the given moment-of-inertia value and the correction coefficient is decreased. 
     
     
       10. The electric-motor control device according to  claim 6 , wherein the condition includes a case in which a predetermined period has not elapsed after at least any one of the given moment-of-inertia value and the correction coefficient is decreased. 
     
     
       11. The electric-motor control device according to  claim 7 , further comprising a disturbance observer,
 wherein the predetermined period is defined based on a time constant in the disturbance observer. 
 
     
     
       12. The electric-motor control device according to  claim 8 , further comprising a disturbance observer,
 wherein the predetermined period is defined based on a time constant in the disturbance observer. 
 
     
     
       13. The electric-motor control device according to  claim 9 , further comprising a disturbance observer,
 wherein the predetermined period is defined based on a time constant in the disturbance observer. 
 
     
     
       14. The electric-motor control device according to  claim 10 , further comprising a disturbance observer,
 wherein the predetermined period is defined based on a time constant in the disturbance observer. 
 
     
     
       15. The electric-motor control device according to  claim 2 , wherein the condition includes a case in which the difference represents that at least any one of the given moment-of-inertia value and a product of the given moment-of-inertia value and the correction coefficient, is less than a moment-of-inertia value of a single electric motor. 
     
     
       16. An electric-motor control system, comprising:
 the electric-motor control device of  claim 1 ; and 
 an electric motor to be controlled by the electric-motor control device. 
 
     
     
       17. An electric-motor control method, comprising;
 calculating a command value directed to an electric motor based on a command value and a given moment-of-inertia value; 
 detecting a difference between the given moment-of-inertia value and an estimated moment-of-inertia value; 
 changing at least any one of the given moment-of-inertia value and a correction coefficient for the given moment-of-inertia value based on the difference; and 
 restricting a change in at least any one the given moment-of-inertia value and the correction coefficient when at least any one of the given moment-of-inertia value and the correction coefficient is decreased.